1. Technical Field
The present invention relates to a pumping device and, more particularly, to a high power pumping apparatus using a wavelength multiplexed pumping source for optical fiber amplification.
2. Related Art
An optical fiber amplifier is variously used in an optical transmission system, such as a wavelength division multiplexing system.
In general, the output power of an optical fiber amplifier is restricted by the pumping power. In particular, in a single mode optical fiber amplifier in which pumping is performed, the pumping power restricts the output power of the optical fiber amplifier to several hundred milliwatts (mW). Therefore, a multimode exciting diode may be used, together with a cladding exciting optical fiber or a beam-shaper, in order to obtain high power. However, the intensity (brightness) of the output light by use of the multimode exciting diode is much smaller than the intensity of optical light by use of a single mode exciting diode. Such a small light intensity may make it difficult to operate the optical fiber amplifier in high population inversion. High population inversion is necessary for a gain-flattening optical fiber amplifier, an Erbium doped fiber amplifier (EDFA), and a three-level system such as Yb.sup.3+ doped optical fiber laser emitted at a wavelength of 980 nm.
Another method of using the high power diode pumping is to use many diodes.
However, this method employs a polarization multiplexer, and that device is quite expensive and is difficult control with respect to its power.
Still another method for optical fiber amplification involves the use of a multi-point injection method. However, this method has problems in that splice loss is generated and the absorption length of the pumping light is reduced. As a result, a lower population inversion, a low gain and a high noise figure are experienced.
Therefore, there is a need for the development of a high power pumping device by means of which it is possible to increase the power of pumping light by increasing the bandwidth of the pumping light. Moreover, there is a need for the development of a high power pumping device which generates stable pumping light by selecting the wavelength of the pumping light using a predetermined reflector.